Emergence and predominance of novel influenza A (H3N2) subclade (3C.2a1b.2a.2a.3a.1) in Kenya and globally in 2023

We report emergence and predominance of the influenza A (H3N2 ) subclade 3C.2a1b.2a.2a.3a.1 in Kenya similar to the global clade in 2023. The Kenyan 3C.2a1b.2a.2a.3a.1 viruses have >15 amino acid differences in the HA and NA proteins relative to 2023/24 WHO recommended Northern/Southern Hemisphere influenza vaccine strains. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by The Wellcome, UK (grant nos. 226002/A/22/Z and 220985/Z/20/Z), New Variant Assessment Programme, a UK Health Security Agency program funded by the UK Department of Health and Social Care as a global initiative to strengthen genomic surveillance for pandemic preparedness and response to emerging and priority infectious diseases; the UK National Institute for Health and Care Research (project references 17/63/82 and 16/136/33) that uses aid from the UK government to support global health research; UK Foreign, Commonwealth and Development Office. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethical approval for the study protocol was obtained from the Scientific and Ethics Review Unit (SERU number 1858) ethics committee, Kenya Medical Research Institute, Nairobi, Kenya. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data generated and analysis script for this manuscript are available from the Virus Epidemiology and Control, Kenya Medical Research Institute (KEMRI)Wellcome Trust Research Programme data server:, Full-length viral genomes are available in GISAID EpiFlu (accession nos EPI\_ISL\_18560856 - EPI\_ISL\_18560859 and EPI\_ISL\_18560907 - EPI\_ISL\_18560947)